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Quadrupedal Mechanics - Anatomy & Physiology (view source)
Revision as of 09:53, 27 April 2013
, 09:53, 27 April 2013→2 Elasticity: external forces and stored energy
:::::Collagen fibrils, sectioned longitudinally and transversely (from Deane, Massey thesis, 1991).
:::::Collagen fibrils, sectioned longitudinally and transversely (from Deane, Massey thesis, 1991).
'''Collagen matures with age'''
Stable aggregations of collagen molecules to form fibrils are achieved by cross-linking of the molecules. These give collagen both strength and elasticity. In newly formed collagen, the cross-links are relatively few, but with age, there is a significant increase in the number and the stability of the cross-links. This has two significant effects. Excessive stress on immature collagen contributes to tendon and ligament disease in young animals; the training of horses especially must take the aging of collagen into account. Also, variations in collagen cross-links cause the toughness associated with different cuts of meat, and with the increase in toughness in meat from older animals.
[[File:QMSection2.10.png|thumb|'''Fig. 2.10 Collagen cross-links''']]
:::::'''Fig. 2.10 Collagen cross-links'''
:::::Crosslinks in immature connective tissue pass between collagen molecules within a fibril (a). The molecules are linked head to tail to form an infinite polymer.
::::In a mature collagen fibre, (b), the crosslinks pass between the fibrils to link them in register.
:::::(Adapted from Bailey, 1988).
[[File:QMSection2.11.png|thumb|'''Fig. 11 Tensile stress in collagen''']]
::::'''Fig. 11 Tensile stress in collagen'''
::::The stress–strain relationship in a bundle of collagen fibres, at a low rate of strain.
::::Phase I: Rapid elongation as the "crimp" in the collagen fibres is eliminated. This part of the curve is smaller at the high strain rates likely to occur in vivo.
::::Phase II: Stress is proportional to strain. This elastic phase of collagen is the phase most useful in vivo.
::::Phase III: Breakdown of the crystalline components of the collagen fibres. Deformation takes place with progressively less stress.